Nuclear medicine is a unique medical specialty wherein radiation is used to acquire images which show the function and anatomy of organs, bones or tissues of the body. Radiopharmaceuticals are introduced into the body, either by injection or ingestion, and are attracted to specific organs, bones or tissues of interest. Such radiopharmaceuticals produce gamma photon emissions which emanate from the body and are captured by scintillation crystals with which the photons interact to produce flashes of light or events. In SPECT (Single Photon Emission Computed Tomography), events are detected by one or more collimated gamma photon detectors, which are typically rotated about a patient's body at a number of different view angles to collect projection data from each view angle. Using the projection data that is collected, three-dimensional images of the organs of the body, which have been taken up the radiopharmaceuticals, e.g. the heart, can be reconstructed.
While SPECT is a powerful tool in the clinician's toolbox, it suffers from at least one drawback—SPECT imaging can be time consuming when compared with other types of imaging procedures. For example, whereas CT (Computed Tomography) x-ray scanning procedures can take as little as a minute to complete, SPECT procedures can take more than fifteen minutes to complete. This is problematic because it can result in patient discomfort which can make it difficult for a patient to remain still during scanning procedures, which can ultimately affect image quality. Similarly, some patients may be unwilling to undergo scanning procedures that take long periods of time.
The amount of time that it takes to scan a patient using SPECT is dependent upon a number of factors. Most significantly, however, is the fact that SPECT detectors include collimating devices that only allow gamma photons traveling along precise trajectories to interact with the detectors. As a result, it can take extended time periods for a sufficient number of gamma photons to interact with the detectors to produce an image. Other factors affecting SPECT scanning time include, but are not limited to, the distance between the object being scanned and the detector(s), the amount of tissue between the object and the detector(s), and the number of different angles of orientation of the SPECT detectors with respect to the object being studied needed to acquire a sufficient number of planar image data from which to reconstruct tomographic images. Further factors affecting SPECT scanning time is that, in many cases, the scanning trajectory is often manually determined by measuring the position of the detector(s) relative to the patient. Such manual processes can be cumbersome and can take several minutes to perform. Finally, manually calculated trajectories may not be optimal or geometrically efficient for the particular scan that is to be performed and/or the specific object that is to be scanned, which can further negatively effect scan time and image quality.
What is needed then is a method for optimizing the trajectory of a SPECT detector(s) about an object or patient to be scanned so as to reduce the overall scan time and patient-on-bed time to thereby enhance image quality.